Stuck Hatch Ends NASA’s Spacewalk Plans

NASA decided Saturday it wasn’t worth the risk to let astronauts try to pry open a jammed space shuttle hatch, and canceled all spacewalks for Columbia’s mission.

Mission Control was concerned that if astronauts Tamara Jernigan and Thomas Jones forced the hatch open, they might not have been able to close it with a tight seal after their spacewalk.

Without such a seal, the chamber between the crew cabin and the open cargo bay could not be repressurized, and the spacewalkers would be stuck outside the cabin.

Two spacewalks had been planned for Columbia’s 16-day flight to test tools and techniques for building a space station.

*

NASA decided to focus instead on how to open and close the hatch in the unlikely event an emergency spacewalk is needed to close the cargo bay doors before returning to Earth. The chance of that happening is extremely low; such an emergency spacewalk has never been required in 15 years of shuttle flight.

Jernigan and Jones were ready to use two crowbar-like tools if asked to go out Saturday night. Flight controllers went down to the wire in making their decision just before the astronauts woke up Saturday afternoon.

Engineers are perplexed as to why the handle on the hatch would not swing into the “unlock” position before the first planned spacewalk on Thursday. On Friday, they suspected the door might be slightly out of alignment and that the astronauts might be able to shove it back into place. But that situation could not be duplicated with equipment on the ground.

Their latest best guess: some sort of jam in the gear mechanism to which the handle is attached. That would be unfixable in orbit.

Besides wanting to avoid further damage, NASA opted against brute force so engineers could inspect the hatch, as is, after the flight.

With the second mission to service the Hubble Space Telescope just three months off--four spacewalks are planned--NASA wants to understand the hatch problem as soon as possible to make sure it does not happen again.

As for the practice spacewalks, NASA will try to squeeze them in on another shuttle mission before Ross and four other astronauts take off in December 1997 on NASA’s first station-assembly flight. If that’s not possible, NASA will have to rely on ground tests and hope for the best, Ross said.